Cooling system



Feb. 13, 1940. G. L. USSELMAN El AL COOLING SYSTEM Original Filed Dec. 12, 1936 2 Sheets-Sheet 1 SUPPLY 'INVENTORS G. L. USSELMAN AND BY c. w. HANSELL 7 5W A ORNEY Feb. 13, 1940.

G. L. USSELMAN El AL 600mm SYSTEM Original Filed Dec. 12, 1936 2 Sheets-Sheet 2 v 1 INVENTORS G. L. USSELMAN m BY c. w. H NSELL ATTORNEY Patented Feb. 13, 1940 PATENT OFFICE- 1 COOLING SYSTEM- George Lindley Usselman, Port Jefferson, and

Clarence W.

Hansell, Rocky Point, N. Y;, as-

signors to Radio Corporation of America, a corporation of Delaware Application December 12, 1936, Serial No. 115,492

1 Renewed July 11, 1939 11 Claims. (01. 250-215, Y1 r1 1 This invention relates to an improved cooling system for tubes. 1 1

. An object of this inventionis to provide a simplified and improved cooling system for rectifier tubes, particularly those of the mercury vapor type. 1

1 Another object of this invention is to improve the operating reliability and life of rectifier tubes H generally. 1 The present 1 system uses a special type of socket for blowing cooling air upward fromthe lower end of the rectifier tubes and an insulating box for controlling the flow of the air about therectifier tubes. Two thermostats, a blower and ia motor-driven damper are used to regulate the temperature of the air passing by the tubes. There is also provided an electrical control circuit to operate this apparatus.

The present temperature control system has ""several advantages over the ordinary system. In

,t-he first place, the cool air during the running period is forced by the blower to pass by the lower end of the tubes first and the heated air then rises, due to forced draft and to natural circulation. This insures that the mercury condensation will be at the bottom of the tube where it should'be. Mercury condensation in any upper part of the tube is likely to result in or cause arcback. That is, if any mercury condenses on the w anode or falls on it from some upper part of the tube, the anode may act like a cathode when an alternating potential is applied to it from the plate transformer and consequently conduct current in both directions through the rectifier tube. These arc-backs are very destructive to the tubes and other parts of the rectifier; 1

A- second advantage is as follows: When the rectifier is shut down, that is, whennot delivering plate potential, the blower is shut down. In

"this condition, the temperature in the box is maintained by a thermostat which turnson and off reduced or normal filament power in the rectifier tubes at various intervals to maintain the air in the box and, the tube envelopes at anapproxilmounted a damper 24 with t deflector 25; M;

Damper 24 is operated by reversible motor 26.;

45 mately desired constant average temperature,

Since the warm 'air in the box will rise, due to convection, the lower end ofthe tubes will be the cooler, which is to be desired as stated above. Also, since the filaments in the rectifier tubes are also used as the box heaters they, being situated directly under the anodes, are very effective in preventing mercury condensation on the anodes, and thereby prevent arc-backs which are ordinarilymost prevalent at or about the time when 55% the rectifier first starts delivering plate voltage,

Another advantageous feature of, this invention; resides in controlling the temperatures of the air forced past therectifier tubes, which isyaccomplished by means of a thermostatically controlled damper, a blower and an insulated box. I

Other desirable features and advantages of this invention will appear from the more detailed description givenv hereinbelow and with, reference to the accompanying drawingsQ wherein: p s 1, m

Fig. lis a schematic showing of my improved cooling system; 1

Fig. 2 is an elevation partly in section. ofa rectifier socket; and 1 Fig. 3 isa plan view of Fig. 2.

Referring now in detail to Fig. 1, the "insu 1 lation covered box I and blower 2 form the, e3 terior portion of the unit. The box is fitted withi an access door 3 for exchanging the rectifier tubes 4-. Each tube is carried or supported by special tube socket 5 which in turn is supported f by some sort of high voltage'insulator 6. The

, anode l of tube 4 is connected through leadft which passes through insulator 9 to a plate trans former circuit represented by It). The cathode;

l! is connected at the base of the tube through tube socket 5 to filament" transformer l2"by means of leads l3 which pass through a close fitting insulating tube l4. The box l is fittedin-j side with lower partition l5 and upperpartition j j l6. There are several'holes II with removable, covers IS in partition 15; The upper partition I6}. is also supplied with several: air holes IS. The tube socket 5 is fitted at the bottom as shown with an insulating air duct or tube 20, which ex- 3 tends through a hole 2| in the lower partition l5; 1 On the back wall inside of box I and located at about the same height as the lower part of tube l, is mounted thermostat 22 used for temperature regulation of the box by means of heatfromj mounted air duct 23 which is connected to the air intake'52 of blower 2. In air duct 23; is

Also, on the damper shaft 21 is mountedadjust-I v able eccentric cam 28. This cam engages rod 29 'whichcontrols the making and breaking of con-, tests 38 and 3! of a second-,thermostat132. The middle or movable contact 33 of thermostat 32 located between fixed contacts 30 and 3|. The latter contacts, are carried on a triangular base member 34. Thermostat 32 is mounted-in the,

output ductSB ofblower 2. This outputduct is 5;;

cathodes H. on the back part of box .I. is

10 v by lead 41 and to power bus 43 by lead 48,

' air duct connection cap to remove any high voltage anode power when the connected to the lower chamber in box I. Blower 2 is driven by a second motor 35.

The damper motor 26 is driven and controlled by transformer 31 and thermostat 32 through leads 3B, 39, 40, 4|, as shown in Fig. 1. Transformer 31 is connected to the 220 volt, .60 cycle supply leads 42 and 43 by leads 45 and 46, as shown. The direction of rotation of motor, 25

' is governed by the position of movable contact 33.

Blower motor 35 is connected to power bus 42 through contact 59 of start-stop relay 49 and lead 52, as shown. Start-stop relay 49 is connected to the positive lead of the output circuit and to filter condenser 58 with bleeder resistor 59 through the center tap of filament transformer l2 and reactor 51. The anode l of tube 4 as shown by Fig. 1 is connected through lead 8 to the secondary of transformer iii. The center tap of transformer I9 is connected to the negative lead of the output circuit and to the filter condenser 58 with bleeder resistor 59.

Fig. 1 is only a schematic cross-section; the ends of box I are parallel to the plane of the paper, that is, one endis near the observer and the other end is away from the observer, the.

1 figure being made simple in order to aid clear explanation. This, however, may introduce some uncertainty in mechanical construction and electrical circuits. -For instance, plate transformer "land the output circuit in general is shown schematically whereas in an actual rectifier the circuits may be more complicated. Likewise, Fig. 1 shows only one tube whereas a rectifier unit in' practice may comprise two, four, six, or even more tubes. In such a unit, the tubes are A placed adjacent each other forming a row, that is, the observer in this case is looking at a row of tubes. end-on. One rectifier, in which this invention was put into commercial practice employed four tubes, another employed six tubes.

, Another difference whichmay be pointed out in 1 is that in actual practice the holes I! in lower partition l5 arelocated between the holes 2!, i. e., between the tubes. There are many other features not shown in Fig. 1 such as in the door 3 there are located two or three glass winfilament power has been applied. Also, in practice door 3 is equipped with electrical interlocks door is open.

Figs. 2 and 3 show an assembly and sectional :view of the special tube socket. The metallic body of the socket i! is supported by the lugs 102. On the lower part of body It! is fitted N13. The two parts IM and I93 are fastened together by screws l04, as shown. The body It! and cap I93 also form a clamp to hold insulators I95. The latter insulators hold in place connection clips I95 and conductor strips I01. Clips I96 make the filament connections. Connection clips H36 are made of two inner contact shoes like a split Filament transformer I2 is connected.

are held together by an external sleeve 196A. A

The two inner contact shoes fiat curved spring 195B is fitted between the external sleeve 156A and an inner shoe to insure good contact. A pin H is driven in contact shoes Hi6 and serves to hold the shoes in place, so that the loose shoe will not pull out ofposition. A screw 38 also holds the two insulators Hi5 and the contact clip assembly together. It should be noted that both parts NH and IE3 are slotted to admit assembly of the contact clips I96, 19? and insulators I95. It should also be noted that insulators W5 are made with shoulders to hold them in position in the socket. The three ribs I99 shown in Fig. 3 are for the purpose of holding the tube 4 in position, leaving a clearance space between the tube base H9 and the tube socket body l9l, for air flow. The arrows show the path of air flow in the socket and upward around the tube envelope. The lower end of part 193 is made to fit inside an air duct, the latter preferably being made of insulating material, such as Bakelite, glass or mica. Parts HM, I92, I93, I94, i945, lill, M8, M9 maybe made of any suitable metal, such as brass, copper, aluminum and iron. Parts :05 may be made of some suitable insulating material, such as Micalex or Isolantite, glass or porcelain.

The operation of this invention is as follows: Assume that in Fig. 1 rheostat 54 has been adjusted to give correct filament voltage when contact 5| ofrelay 49 was closed. In the shutdown condition, relay 49 is deenergized and contacts 59 and 51 are open. Blower Zand motor 35 are shut down, reduced or approximately normal filament power is applied intermittently through resistors 55 by means of the.

contacts of thermostat 22. The value of resistors 55 may-be changed to suit summer or winter operation, i. e., less resistance being required for winter operation. This may be arranged so that two resistors may be used in parallel for winter and one may be used for summer operation. The thermostat 22 by virtue of being connected in series with the voltage supply resistances 55 and the primary of filament transformer l2 turns the filaments ,I I off and on at such a rate as to heat and hold at a fairly constanttemperature the air in the box about the region of the lower half of the tubes. The heat insulation on the box i helps to hold this temperature constant. The slight amount of air convection in the box is suflicient to keep the air in the top part of the box hotter than that in the lower part. This fact, coupled with the fact that the filaments are used as the box heaters, has an important beneficial influence on the operation of the rectifier tubes, for the following reasons.

For best operation to prevent arc-back and to promote a long tube life, (1) the tube temperature should be kept within from 35 to 40 C.

, This means that when the tubes are operating or are started in operation as rectifiers, this temperature should be maintained. (2) Also, to prevent arc-back, no condensed mercury should be allowed to collect on the anode or to fall on it during the time when anode voltage is applied.

The first point requires substantially constant tube wall temperature of the correct value to insure constant mercury vapor pressure of proper value, which is a factor in the arc-back tendency of a mercury vapor rectifier tube. The second point requires that the upper part of the tube and the "anode :be: kept at a higher temperature than the lower part of the:tube, so that all :mercury .can'fall orcollect on the anode during the time 'when'voltageis. applied to it. .In other words,

the heatedfilamenhbeing very close to the anode,

the. latter is kept hotter than the envelope of the tube. Also, as stated before, the fact that the .air in the upper part of the box is warmer than that in the lower part insures that no mercury vapor will condense on the upper wallsof the "tube.

.During the shutdown period, damper .24 and its controlim-echanism is still in operation and inthe summer time this damper would, in most cases, not-move but during coldweather it would close because thermostat 32 would gradually become cooled ofi since the blower is not running in the shutdown condition.

When the rectifier is to be started for delivering plate power in the form of rectified, that is, direct current, the control switch or relay 53 is closed which in turn closes start-stop relay 48. i This closes contacts 5!] and 5! and other contacts, not shown, for applying plate voltage. This applies steady full normal filament power because resistors 55 and thermostat 22 are short-circuited by contact 5!. The closing of contact 50 causes the blower to function. After the filament has had full power applied for about one minute, anode voltage is applied from plate transformer l0. H

When the blower 2 is operating, air is forced into duct 36 past thermostat 32 and into the lower chamber of box formed by lower partition 15. The air is then forced up through tube 28 into tube socket 5, where it comes in contact with and flows up along the tube wall absorbing heat as it passes upward. Since the air becomes more heated and consequently absorbs less heat as it travels toward the top of the tube, the upper part of the tube will be warmer than the lower end of the tube. This warm air passes through the holes l9 in the upper partition 16, out and down through the duct 23 to'the blower intake 62 where it is againcforced into the lower duct 3'5 past thermostat 32 and up through the tube socketfi, and so on. I

After a number of these air cycles, the circulating air will absorb extra heat and become heated due'to the higher filament power now in use and This rise in air temperature passing thermostat 32 will cause it to function to move contact 33 against (assume) contact 38. This will cause motor 26 to rotam the damper 24 in ,a clockwise direction opening up the damper so that some warm air passes out at the top of the damper and a. like amount of cool air passes into the blower at the bottom of the damper. The action of cam 28 and rod 2d moves the contact carriage 34 and contact 35 is then moved away from contact 38. This latter action stops the damper movement until contacts! and 3b are again made. In other words, cam 28, rod 29 and contact carriage '34 act as a stabilizer to prevent hunting andtoo frequent operation of the damper. straining the thermostat elements. The curved part 25 of damper 24 is for the purpose of deflecting the outgoing warm air away from the lower or cool air intake. In other words, it makesthe damper more efiicient; there are baffle plates or side shields, not shown in the sketch, on each side of damper to prevent the heated air from get- It also prevents ting. back into the ventilatingsystem around the air is sufiiciently cooled. Should the air which is forced up through tube socket 5 becometoo cool,

contacts 33 and ti of thermostat '32, will close, which will cause the damper toclose as long as contact is being made; so that less cool air is taken in from the outside. When the airis sufilciently cooled, the'action of cam 28 and rod 29 moves carriage 34 and contact 3l. away from central contact 33 and so on, until a stable tem perature is obtained by proper opening of the damper 24. i

The action of cam 28 (on damper shaft 21) through rod 29 and the contacts 30, 3| and 33 is to refine and make the operation of thermostat 32 and damper 24 more accurate and more sensitive. The damper moves only when the thermostat 32 and contact 33 is moving because when contact 33 is stationary, contact 30 or 31" is backed ofi by the cam arrangement (which breaks contact with 33). This is accompanied by a like movement of the damper. Thus, when the temperature of the air passing thermostat 32 is substantially constant, contact 33 is floating between contacts 38 and 3!, touching neither one Any small change in blower output air temperature will quickly be corrected by thermostat 32 and the damper 24. 1

Extra openings ll with removable covers 18 have been provided to increase the air circulation in the box i if the air circulation is not sufficient during hot weather or in hot climates.

The damper motor 26 is provided with limit switches (not shownl which limit its range of rotation to ninety degrees, so that damper M can operate in any position from closed to full open:

The box I is usually constructed with a metal I frame. and the walls are made of some suitable heat and electrical insulating material such as asbestos, fire-proof material being preferable.

When the transmitter shuts down, start stop relay 49 opens contacts lit and 5!, after plate power has been removed. This-shuts ofi the blower and the temperature control isresumed by thermostat 22 through intermittent filament heating. r

While only one form of cooling device is shown, it is to be distinctly understood that this invention is not to be limited to this form of device but due to the tube losses in conductlngplate current. i

may include other modifications.

What is claimed is: I 1. A system for regulating the temperature of as a a mercury vapor rectifier tube having a quantity of mercury subjected to condensation normally.

located within the lower portion thereof whereby arc-backs in said tube are prevented by keeping the anode and upper portion of said tube 'free from condensed mercury vapor, comprising temperature responsive switching means adjacent said tube, and means responsive to said switchin said tube, a housing enclosing said mercury vapor tube, a tube socket device within said housing having an air passage arranged between the base of the tube and the side walls of said socket, and means comprising a blower adjacent said housing for controlling the temperature of air entering said passage.

3. In combination, means for regulating mercuryvapor rectifier tube temperatures by regulating the heat on the cathode of the tube during the time the anode voltage of the tube is shut off, a second means for regulating the tube temperature by circulating air around the outside of said tube when the anode voltage is applied, and a third means rendering the first of said means inoperative during the time the anode'voltage is applied.

"4. In a rectifier system including the combination of-a blower for forcing temperature regulated air through a tube socket device and up and 1 around the envelope of a vapor filled tube, a tube compartment enclosing said tube, means for controlling the air temperature by the use of a thermostatically controlled damper for taking in and mixing a portion of cooled air with the warm air of the tube compartment, and means for causing the mixed air to pass over the temperature regulating thermostat, and a second temperature regulating device within said tube compartment for controlling the temperature on the cathode of said tube when said blower is inactive.

5. In a system for temperature regulating an electron discharge device mounted within a container, said device having an anode and a cathode, a damper mounted in a wall of said container for controlling air temperature within said container, a blower outside said container, a cam mechanism, a thermostat associated with a rod engaging said cam, said rod controlling a pair of contacts located each side of a middle contact on said thermostat, the combination of said thermostat, rod, and cam operating to control the blower air output temperature, said cam mechanism being arranged to prevent over-travel or hunting of the damper and to prevent distortion of any of the thermostat elements.

6. A temperature regulating system comprising an electron discharge device having an anode and cathode, a container for said device and a pair of thermostats located within said container, one of said thermostats being arranged to control the temperature within said device and the surrounding air temperature outside said device when anode voltage is absent, the other one of said thermostats arranged to control a means for maintaining the temperature of said anode and surrounding air temperature when anode voltage is present.

'7. A system for regulating the temperature and vapor pressure or" an electron discharge device having at least an anode and cathode, an insulating housing for said electron discharge device, tube socket for inserting the base of and supporting said device insulatingly supported within said housing, said socket having a space'between its inner walls and the base of said device for the passage of air fiow up past the said base and around the envelope of the said device, and a plurality of guides integral with the inner wall of said socket for supporting the electron discharge device centrally in said socket and to allow equal flow of air all around the said device for ventilatmg purposes.

8. A system for regulating the temperature of a mercury vapor rectifier tube having a quantity of mercury subjected to condensation normally located within the lower portion thereof, said rectifier tube having at least anode and cathode circuits, a power supply for heating said cathode circuit, a thermostat and a resistance in series with said power supply, and external means responsive to the action of said thermostat for partially heating said cathode through said resistance when said anode circuit is inactive to keep the condensation of said mercury in the lower portion of said tube.

9. The method for preventing condensation of mercury on the electrodes of a mercury vapor rectifier tube, including the steps of maintaining the electrodes at a higher temperature than that at which mercury condenses during idle periods prior to the operation of said rectifier, and maintaining said rectifier at a higher temperature than that at which mercury condenses during the operation of the rectifier.

10. The method as claimed in the preceding claim characterized by the fact that the temperature of said rectifier is maintained substantially constant at a value substantially higher than that at which mercury condenses both prior and during operation of said rectifier tube.

11. A system for regulating the temperature of a mercury rectifier tube having a quantity of mercury subjected to condensation normally located within the lower portion thereof, whereby arcbacks in said tube are prevented by keeping the anode and upper portion of the tube free from condensed mercury vapor, comprising temperature responsive switching means adjacent said tube and means responsive to said switching means for controlling the heating power supplied to the cathode of said tube in such a way that the anode and upper portion of the tube are maintained at a temperature unsuitable for condensation of mercuryv thereon, and means for directing cooling fluid around the base of said tube whereby any condensation which does take place occurs at the base of the tube away from the anode of said tube.

GEORGE LINDLEY USSELMAN. CLARENCE W. HANSELL. 

